Hot module for fuel cell system

Abstract

To provide a hot module of a fuel cell system capable of miniaturizing a reformer by reducing the used amount of a catalyst.SOLUTION: A hot module of a fuel cell system includes: a reformer 2 of a double cylinder structure having a catalyst filling layer 23 between an outer cylinder 21 and an inner cylinder 22; a heat radiation cylinder Za inserted into the inner cylinder 22 so that surfaces are separated from each other; a burner 3 connected to the heat radiation cylinder Za; a cell stack assembly 61 in which a plurality of fuel cell stacks 1 are integrated; a first distribution manifold Ma serving as an introduction mother pipe of anode fuel Gc; a second distribution manifold Mb serving as an introduction mother pipe of cathode air Aa; a first collection manifold Mc serving as a lead-out main pipe of anode off-gas Gd; and a second collection manifold Md serving as the lead-out main pipe of cathode off-gas Ge. The hot module is configured by arranging a cell stack assembly 61, the first collection manifold Mc, and the second collection manifold Md so as to surround the outer cylinder 21.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a hot module of a fuel cell system.

Background Art

[0002] Conventionally, various types of fuel cells have been developed as power generation devices that emit fewer environmentally harmful substances and have excellent power generation efficiency compared to gas turbine generators and gas engine generators. In particular, solid oxide fuel cells (SOFCs) can achieve a high power generation efficiency of 50% or more, and are thus used for power generation in a wide range of output ranges from industrial to household applications.

[0003] Fuel cell systems include a reformed type that uses methane-containing gas such as city gas as a primary fuel and a non-reformed type that uses hydrogen as a primary fuel. In Japan, since the hydrogen supply infrastructure is still under development, the former is the mainstream. In a reformed fuel cell system, it is mainstream to generate reformed gas using an endothermic external reformer with a steam reforming catalyst. Together with the cell stack that is the core of power generation, auxiliary devices such as reformers and combustors are packaged to form a thermally self-sufficient hot module. To supply the heat required for the steam reforming reaction, as disclosed in Patent Documents 1 to 3, mainly the combustion heat of low-calorie off-gas and / or high-calorie primary fuel is utilized.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] The fuel cell system described in Patent Document 1 has a configuration in which a cylindrical reformer is placed inside a hot module, and combustion heat is supplied from the inside of the reformer through heat conduction via the wall surface, while waste heat is supplied from the outside of the reformer through radiant heat transfer from the cell stack. The fuel cell systems described in Patent Documents 2 and 3 both have a configuration in which a cylindrical reformer is placed inside a hot module, and combustion heat is supplied from the inside of the reformer through heat conduction via the wall surface, while waste heat is supplied from the outside of the reformer through radiant heat transfer from the cell stack and convective heat transfer of the cathode-off gas. The waste heat supplied from the outside of the reformer is the heat generated by the power generation reaction in the cell stack, and is mainly due to the reaction energy of hydrogen and / or carbon monoxide and oxygen, and the energy loss of the power generation cell.

[0006] Incidentally, the operating temperature of SOFC cell stacks has decreased from the previous 700-900°C to 500-700°C in recent years due to improvements in materials and structure. As the operating temperature of the cell stacks decreases, the amount of waste heat supplied from outside the reformer decreases, which tends to reduce the efficiency of the steam reforming reaction and increase the amount of catalyst used.

[0007] This invention has been made in view of the above problems, and aims to provide a hot module for a fuel cell system that enables miniaturization of the reformer by reducing the amount of catalyst used. [Means for solving the problem]

[0008] The hot module according to the present invention comprises a reformer having a double-cylinder structure with a catalyst packed layer between an outer cylinder and an inner cylinder, a heat radiation cylinder inserted into the inner cylinder so that their surfaces are spaced apart, a burner connected to the heat radiation cylinder, a cell stack assembly comprising a plurality of fuel cell stacks, and an anode fuel introduction main pipe arranged along the reformer, wherein the fuel cell cell A first distribution manifold connected to each of the stacks via branch pipes, and a cathode air introduction main pipe arranged along the reformer, the fuel cell cell A second distribution manifold connected to each of the stacks via branch pipes, and an anode off-gas outlet main pipe arranged along the reformer, the fuel cell cell A first collection manifold connected to each of the stacks via branch pipes, and a cathode-off gas outlet main pipe arranged along the reformer, the fuel cell cell The cell stack assembly, the first collection manifold, and the second collection manifold are arranged near the reformer and surrounding the outer cylinder, so that waste heat contained in the anode-off gas is supplied to the reformer from the first collection manifold and waste heat contained in the cathode-off gas is supplied to the reformer from the second collection manifold. With this configuration, it is possible to reduce the size of the reformer by reducing the amount of catalyst used.

[0009] More specifically, the above configuration involves arranging the first distribution manifold and the second distribution manifold adjacent to each other and in the vicinity of the cell stack assembly. This configuration allows heat exchange to occur between the surfaces of the first distribution manifold, the second distribution manifold, and the cell stack assembly. This configuration is also acceptable. With this configuration, the temperatures of the anode fuel and cathode air supplied to the cell stack are made uniform and raised to near the operating temperature of the cell stack, making it possible to carry out an efficient power generation reaction throughout the entire power generation cell.

[0010] More specifically, the above configuration is as follows: fuel cell A cell stack consists of a predetermined number of flat-plate power generation cells stacked between a pair of end plates. The aforementioned The end plate has a port for anode fuel inflow, a port for cathode air inflow, a port for anode off-gas outflow, and a port for cathode off-gas outflow, and each of these ports is connected to the corresponding first distribution manifold, second distribution manifold, first collection manifold, and second collection manifold. The aforementioned The pipes are connected via branch pipes, each of which has a pipe length longer than the shortest distance connecting the port and the manifold, and may also include curved sections. With this configuration, the expansion and contraction of the pipes can be absorbed in the curved sections, making it possible to avoid the generation of thermal stress.

[0011] More specifically, in the above configuration, the curved portion The cross-sectional centers of the branch pipes are located in the same plane throughout the entire curved section. may have a planar pipe structure. According to this configuration, the expansion and contraction of the pipe occurring in a predetermined two-dimensional direction (for example, the horizontal direction) can be effectively absorbed.

[0012] Also more specifically, in the above configuration, the curved portion The cross-sectional viewing centers of the branch pipes do not fall within the same plane throughout the entire region of the curved section. may have a three-dimensional pipe structure. According to this configuration, the expansion and contraction of the pipe occurring in the three-dimensional direction can be effectively absorbed.

Advantages of the Invention

[0013] According to the hot module according to the present invention, miniaturization of the reformer can be achieved by reducing the amount of catalyst used.

Brief Description of the Drawings

[0014] [Figure 1] It is an explanatory diagram showing the configuration of the fuel cell system 100 according to the present embodiment. [Figure 2] It is a perspective view of the hot module HM according to the present embodiment. [Figure 3] It is a perspective view of the hot module HM with a part not shown. [Figure 4] It is a perspective view of the hot module HM with a part not shown. [Figure 5] It is a perspective view of the hot module HM with a part not shown. [Figure 6] It is a perspective view of the hot module HM with a part not shown. [Figure 7] It is a side view of the hot module HM with a part not shown. [Figure 8] It is a side view of the hot module HM with a part not shown.<X000095> [Figure 9] It is a side view of the reformed gas generator RG according to the present embodiment. [Figure 10] It is a side cross-sectional view of the reformed gas generator RG. [Figure 11] This is a diagram showing the configuration near the burner in the reformed gas generator RG. [Figure 12] This is a side view of the hot module HM, with some parts omitted from the illustration. [Figure 13] This is a perspective view of the cell stack 1 according to this embodiment. [Figure 14] This is a perspective view of the cell stack 1 according to this embodiment. [Figure 15] This is a plan view of cell stack 1. [Figure 16] This is a perspective view of the stack assembly 61 according to this embodiment. [Figure 17] This is a perspective view of stack assembly 61. [Figure 18] This is an explanatory diagram showing a unit rack with Cell Stack 1 installed. [Figure 19] This is an explanatory diagram of a branch pipe extending from a manifold according to this embodiment. [Figure 20] This is an explanatory diagram regarding the connection configuration of each power terminal of cell stack 1. [Figure 21] This is a diagram showing the configuration of the plate assembly 80 according to this embodiment. [Figure 22] This is a perspective view of the heat transfer plate 81 used in the plate assembly 80. [Figure 23] This is an explanatory diagram regarding low-temperature fluid channels and high-temperature fluid channels. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the drawings.

[0016] <Overview of Fuel Cell System Configuration> First, an overview of the configuration of the fuel cell system 100 according to this embodiment will be described. Figure 1 is an explanatory diagram showing the configuration of the fuel cell system 100. As shown in Figure 1, the fuel cell system 100 comprises a plurality of cell stacks (fuel cell stacks) 1, a reformer 2, a burner 3, an evaporator 4, an air preheater 5, an anode off-gas cooler 6, an anode off-gas condenser 7, a CO oxidizer (carbon monoxide oxidizer) 8, a condensate recovery tank 9, a first fuel blower 10, a first air blower 11, a water pump 12, a second fuel blower 13, a second air blower 14, a power conditioner 15, and a system controller 16.

[0017] In this embodiment, a total of eight cell stacks 1 are provided, including those not shown in Figure 1. Furthermore, in the following description, the fuel cell system 100 may be simply referred to as the "system."

[0018] The fuel cell system 100 also includes the following lines (pipes): raw fuel line La, mixed gas line Lb, anode fuel line Lc, anode off-gas line Ld, cathode air line Le, cathode off-gas line Lf, combustion gas line Lg, burner cooling air line Lh, reformed water line Li, starting air line Lj, ​​and condensate recovery line Lw.

[0019] The anode fuel line Lc includes a first distribution manifold Ma, which serves as the main line for introducing anode fuel, and the cathode air line Le includes a second distribution manifold Mb, which serves as the main line for introducing cathode air. These distribution manifolds Ma and Mb have an inlet and multiple outlets corresponding to each cell stack 1, and the fluid that flows into the inlet is discharged from each outlet.

[0020] The anode off-gas line Ld includes a first collection manifold Mc, which serves as the main outlet for the anode off-gas, and the cathode off-gas line Lf includes a second collection manifold Md, which serves as the main outlet for the cathode off-gas. These collection manifolds Mc and Md have multiple inlets and outlets corresponding to each cell stack 1, and the fluid that flows into each inlet is discharged from the outlet.

[0021] The combustion gas line Lg includes the heat radiation cylinder Za and the combustion gas pipe Zb.

[0022] The raw fuel line La is a pipeline connecting the fuel inlet E1 and the burner 3, and a second raw fuel blower 13 is located in this pipeline. The second raw fuel blower 13 is a device that pressurizes the raw fuel gas (e.g., methane-containing gas such as city gas 13A) Gf taken in from the fuel inlet E1 and sends it to the downstream side of the raw fuel line La, and is typically driven during the system's startup operation.

[0023] The mixed gas line Lb is a pipeline connecting the fuel intake E2 and the reformer 2. In this pipeline, from upstream to downstream, the first raw fuel blower 10, the evaporator 4, and the first bellows-type expansion joint B1 are arranged in that order. The first raw fuel blower 10 is a device that pressurizes the raw fuel gas Ga taken in from the fuel intake E2 and sends it to the downstream side of the mixed gas line Lb, and is typically driven during the power generation operation of the system.

[0024] The anode fuel line Lc is a pipeline connecting the reformer 2 to the anodes of each cell stack 1. More specifically, the anode fuel line Lc has, in order from upstream, a pipeline connecting the reformer 2 to the inlet of the first distribution manifold Ma, the first distribution manifold Ma, and eight pipelines (branch pipes of the first distribution manifold Ma) connecting each outlet of the first distribution manifold Ma to the anodes of each cell stack 1.

[0025] The anode-off gas line Ld is a pipeline connecting the anode of each cell stack 1 to the burner 3. More specifically, the anode-off gas line Ld has, in order from the upstream side, eight pipelines (branch pipes of the first collection manifold Mc) connecting the anode of each cell stack 1 to the inlets of the first collection manifold Mc, the first collection manifold Mc, and a pipeline (hereinafter referred to as "pipeline Ld1") connecting the outlet of the first collection manifold Mc to the first gas cylinder 31 (described later) of the burner 3. Along pipeline Ld1, in order from the upstream side, are the second bellows-type expansion joint B2, the anode-off gas cooler 6, the anode-off gas condenser 7, and the gas-water separation unit Sa.

[0026] The cathode air line Le is a conduit connecting the air intake E3 to the cathode of each cell stack 1. More specifically, the cathode air line Le consists of, in order from the upstream side, a conduit connecting the air intake E3 to the inlet of the second distribution manifold Mb (hereinafter referred to as "conduit Le1"), the second distribution manifold Mb, and eight conduits (branch pipes of the second distribution manifold Mb) connecting each outlet of the second distribution manifold Mb to the cathode of each cell stack 1.

[0027] In the pipeline Le1, the following components are arranged in order from upstream: a first air blower 11, an anode off-gas cooler 6, an air preheater 5, and a third bellows-type expansion joint B3. The first air blower 11 is a device that pressurizes the air Aa taken in from the air intake E3 and sends it to the downstream side of the cathode air line Le, and is typically driven during the power generation operation of the system. Furthermore, in pipeline Le1, a bypass route Le2 is provided that bypasses the anode off-gas cooler 6 and the air preheater 5, connecting the midpoint between the air intake E3 and the anode off-gas cooler 6, and the midpoint between the air preheater 5 and the third bellows-type expansion joint B3.

[0028] The cathode-off gas line Lf is a conduit connecting the cathode of each cell stack 1 to the burner 3. More specifically, the cathode-off gas line Lf has, in order from the upstream side, eight conduits (branch pipes of the second collection manifold Md) connecting the cathode of each cell stack 1 to the respective inlets of the second collection manifold Md, the second collection manifold Md, and a conduit (hereinafter referred to as "conduit Lf1") connecting the outlet of the second collection manifold Md to the second gas cylinder 32 (described later) of the burner 3.

[0029] The combustion gas line Lg is a pipeline connecting the burner 3 and the gas outlet D1. More specifically, the combustion gas line Lg has, in order from upstream, a heat radiation cylinder Za, a pipeline connecting the heat radiation cylinder Za and the combustion gas pipe Zb, the combustion gas pipe Zb, and a pipeline connecting the combustion gas pipe Zb and the gas outlet D1 (hereinafter referred to as "pipeline Lg1"). Along pipeline Lg1, in order from upstream, are a fourth bellows-type expansion joint B4, an air preheater 5, a CO oxidizer 8, and an evaporator 4.

[0030] The burner cooling air line Lh is a conduit connecting conduit Le1 and the starting air line Lj, ​​and a flow rate adjustment means (such as an orifice) not shown is provided in this conduit. More specifically, the burner cooling air line Lh is a conduit that branches off at an intermediate point in conduit Le1, which connects the first air blower 11 and the anode off gas cooler 6, and merges with the starting air line Lj downstream of the second air blower 14, and is configured so that a small flow rate of air Ab flows toward the burner 3 when the first air blower 11 is driven. As will be described in more detail later, the burner cooling air line Lh can be omitted depending on the combustion temperature of the burner 3.

[0031] The reformed water line Li is a pipeline connecting the condensate recovery tank 9 and the evaporator 4, and a water pump 12 is located in this pipeline. The water pump 12 is a device that sends the condensate Wb stored in the condensate recovery tank 9 as reformed water Wa to the downstream side of the reformed water line Li.

[0032] The startup air line Lj is a conduit connecting the air intake E4 and the conduit Lf1, and a second air blower 14 is located in this conduit. The second air blower 14 is a device that pressurizes the air Ac taken in from the air intake E4 and sends it downstream of the startup air line Lj, ​​and is typically driven during the system's startup operation.

[0033] The condensate recovery line Lw is a pipeline connecting the gas-liquid separation unit Sa, located in the middle of the pipeline Ld1, to the condensate recovery tank 9. The gas-liquid separation unit Sa is a component that separates the condensate Wb generated in the anode-off gas condenser 7 from the anode-off gas Gd, and the separated condensate Wb flows down the condensate recovery line Lw. The tip of the condensate recovery line Lw is open to the gas phase without being submerged in the aqueous phase of the condensate recovery tank 9, so that the amount of condensation does not increase or decrease due to the influence of the water temperature of the stored condensate Wb. The reason for not submerging the tip of the condensate recovery line Lw in the aqueous phase is to avoid changing the flow rate of the anode-off gas Gd sent to the burner 3. This configuration is particularly effective when the anode-off gas Gd after separating the condensate Wb is recycled to the primary side of the cell stack or used for power generation in a subsequent cell stack. For example, the gas-liquid separation unit Sa uses a T-shaped pipe with a straight pipe section arranged horizontally and a branch pipe section arranged downwards. Additionally, a small-capacity cylindrical container erected vertically can be used as the gas-liquid separation unit (Sa).

[0034] Cell stack 1 is a power generation unit composed of solid oxide fuel cells (SOFCs). Solid oxide fuel cells are high-temperature operating fuel cells in which the solid electrolyte, anode, and cathode that make up the power generation cell are all ceramics. A power generation unit formed by integrating a predetermined number of power generation cells via a metal interconnector material (also called a separator material) is called a cell stack. The battery output of cell stack 1 is supplied after being adjusted by the power conditioner 15.

[0035] Reformer 2 uses steam to reform the raw fuel gas Ga, producing reformed gas Gc, which is then sent downstream. Reformer 2 has a catalyst for steam reforming, which reacts the methane contained in the raw fuel gas Ga with steam to produce reformed gas Gc containing carbon monoxide and hydrogen. Although steam reforming is an endothermic reaction, heat supplied from burner 3 allows reformer 2 to stably produce reformed gas Gc.

[0036] Burner 3 burns the incoming gas to generate heat and discharges the combustion gas Gg produced by the combustion into the exhaust gas line Lg. Evaporator 4 is a device that indirectly exchanges heat between the reformed water Wa and the combustion gas Gg (heat source fluid). Through heat exchange with the combustion gas Gg, it evaporates the reformed water Wa and simultaneously heats the raw fuel gas Ga.

[0037] The air preheater 5 and the anode off-gas cooler 6 are both heat exchangers that indirectly exchange heat between a low-temperature fluid and a high-temperature fluid. The air preheater 5 plays the role of preheating the air Aa in the cathode air line Le by heat exchange with the combustion gas Gg, while the anode off-gas cooler 6 plays the role of cooling the anode off-gas Gd by heat exchange with the air Aa in the cathode air line Le.

[0038] The anode off-gas condenser 7 plays the role of cooling the anode off-gas Gd and condensing the water vapor contained in the anode off-gas Gd. In this embodiment, the anode off-gas condenser 7 is an air-cooled heat exchanger, but a water-cooled heat exchanger may be used instead, and the system may be configured as a cogeneration type where heat is recovered by this means.

[0039] The CO oxidizer 8 is a device that converts harmful carbon monoxide contained in the combustion gas Gg into harmless carbon dioxide by contacting it with a catalyst. The CO oxidizer 8 does not operate if the oxidation reaction in burner 3 is complete, and only operates if the oxidation reaction in burner 3 is incomplete.

[0040] The condensate recovery tank 9 plays the role of recovering the condensate Wb discharged from the gas-water separation unit Sa and making it reusable as reformed water Wa. The condensate recovery tank 9 is equipped with a water level detector Sb and a drain valve Sc to adjust the water level of the stored reformed water Wa to a predetermined range. When the water level detector Sb detects the upper limit water level, the drain valve Sc is opened, and when the water level detector Sb detects the lower limit water level, the drain valve Sc is closed. In this way, the required amount of reformed water Wa is secured in the condensate recovery tank 9. In order to prevent anode off gas Gd from leaking to the outside when the reformed water Wa is drained, the drain position by the drain valve Sc is set near the bottom of the condensate recovery tank 9.

[0041] The power conditioner 15 is a device that converts the electricity generated by the cell stack 1 into a form that can be used in business activities and daily life. The power conditioner 15 includes a DC / DC converter (boost circuit) that boosts the DC voltage output from the cell stack 1, a grid-connected inverter (voltage conversion circuit) that converts the DC voltage boosted by the DC / DC converter into an AC voltage synchronized with the grid power supply, an output current control unit (output control circuit) that controls the output current (sweep current) of the cell stack 1, and a drive power supply unit (auxiliary circuit) that supplies drive power to auxiliary equipment.

[0042] The grid-connected inverter described above is electrically connected to the commercial power distribution panel installed within the building. The grid-connected inverter and the distribution panel can be switched between parallel and disconnected connections via a grid-connection switch. The distribution panel is electrically connected to the commercial power supply and multiple distribution boards. Load equipment used within the building, such as lighting fixtures, power units, and outlets, is electrically connected to the distribution boards.

[0043] The above-mentioned drive power supply unit is connected to the spark rods (first electrode rods, described later) of each blower 10, 11, 13, 14, water pump 12, and burner 3, and provides drive power to these auxiliary devices. When the auxiliary devices are DC-driven, the drive power supply unit is configured to supply power obtained by AC / DC conversion of the output of the grid-connected inverter, power obtained by AC / DC conversion of the input from the commercial power supply, or power obtained by DC / DC conversion of the output of the cell stack 1. On the other hand, when the auxiliary devices are AC-driven, the drive power supply unit is configured to supply power obtained by AC / DC conversion of the output of the grid-connected inverter or input power from the commercial power supply. The above-mentioned auxiliary devices are driven using the commercial power supply during system startup and shutdown operations, and are driven using generated power during system power generation operations.

[0044] The system controller 16 is a device that controls the operation of auxiliary equipment such as blowers and the power conditioner 15 (i.e., system operation) according to a control program that has been created and stored in advance.

[0045] As shown by the dashed lines in Figure 1, each cell stack 1, reformer 2, burner 3, each manifold Ma to Md, heat radiation tube Za, and combustion gas pipe Zb are located in the first region R1, which is inside the first box X1 (see Figure 3) in the hot module HM described later. On the other hand, the evaporator 4, air preheater 5, anode off gas cooler 6, and CO oxidizer 8 are located in the second region R2, which is outside the first box X1 and inside the second box X2 (see Figure 3) described later. The anode off gas condenser 7, condensate recovery tank 9, each blower 10, 11, 13, 14, water pump 12, power conditioner 15, and system controller 16 are located outside the hot module HM (in the ambient temperature region).

[0046] <Fuel cell system operation overview> Next, the operation overview of the fuel cell system 100 will be explained with reference to Figure 1. The raw fuel gas Ga supplied from the fuel intake E2 into the mixed gas line Lb is sent to the downstream side by the action of the first raw fuel blower 10. In parallel with the supply of raw fuel gas Ga, the reformed water Wa supplied from the condensate recovery tank 9 into the reformed water line Li has its water volume regulated by the water pump 12 and flows into the mixed gas line Lb.

[0047] The reformed water Wa flows into the evaporator 4 along with the raw fuel gas Ga in the mixed gas line Lb, where it is heated by heat exchange to become steam (superheated steam). This steam mixes with the heated raw fuel gas Ga and flows into the reformer 2 as a mixed gas Gb.

[0048] The reformer 2 uses water vapor in the mixed gas Gb to reform the raw fuel gas Ga, generating reformed gas Gc which is then sent downstream. The reformed gas Gc sent from the reformer 2 is distributed to the anodes of each cell stack 1 through the anode fuel line Lc.

[0049] Meanwhile, in parallel with the supply of the raw fuel gas Ga mentioned above, air Aa is supplied from the air intake E3 into the cathode air line Le. The air Aa in the cathode air line Le is sent to the downstream side by the action of the first air blower 11. This air Aa is heated by heat exchange in the anode off-gas cooler 6, and then heated further by heat exchange in the air preheater 5 before being distributed to the cathodes of each cell stack 1. It is also possible to flow a portion of the air Aa, air Aa1, into the cathodes of each cell stack 1 via the bypass path Le2 for temperature control of the air Aa.

[0050] Furthermore, in synchronization with the supply of air Aa to the cathode, air Ab is supplied to the cooling air line Lh. The air Ab in the cooling air line Lh is sent to the burner 3 by the action of the first air blower 11. This air Ab acts as a coolant to lower the combustion temperature of the burner 3, preventing overheating and burnout of the flame holder 33 (described later). Note that if the flame temperature is maintained at a level that prevents overheating and burnout of the flame holder 33 without supplying air Ab, the burner cooling air line Lh may be omitted.

[0051] Each cell stack 1 generates electricity using reformed gas Gc flowing into the anode and air Aa flowing into the cathode, while simultaneously discharging anode off-gas Gd from the anode to the anode off-gas line Ld and cathode off-gas Ge from the cathode to the cathode off-gas line Lf. The anode off-gas Gd contains fuel components that were unreacted at the anode, and the cathode off-gas Ge contains oxygen that was unreacted at the cathode.

[0052] The anode off gas Gd discharged from each cell stack 1 to the anode off gas line Ld is collected in the first collection manifold Mc, cooled by heat exchange in the anode off gas cooler 6, and then flows into the anode off gas condenser 7. In the anode off gas condenser 7, the anode off gas Gd is cooled to below the dew point temperature, and the water vapor contained in the anode off gas Gd condenses.

[0053] The anode-off gas Gd that has passed through the anode-off gas condenser 7 is sent to the gas-liquid separation unit Sa where gas-liquid separation occurs, and the condensed water Wb is recovered in the condensed water recovery tank 9. The condensed water Wb recovered in the condensed water recovery tank 9 is reused as reformed water Wa, as described above. The portion of the anode-off gas Gd that did not condense (anode-off gas Gd after gas-liquid separation) is sent to the burner 3.

[0054] The cathode-off gas Ge discharged from each cell stack 1 to the cathode-off gas line Lf is collected in the second collection manifold Md, then mixed with air Ab that flows in via the burner cooling air line Lh in pipeline Lf1, and sent to the burner 3. Depending on the operating state of the system, raw fuel gas Gf supplied from fuel intake E1 is sent to the burner 3 via the raw fuel line La, and air Ac supplied from air intake E4 is sent via the starting air line Lj.

[0055] Burner 3 receives gas Gx, which is the raw fuel gas Gf and / or anode-off gas Gd, and gas Gy, which is air Ac and / or cathode-off gas Ge, and burns them to generate heat. Specifically, gas Gx for the first burner is either a mixture of raw fuel gas Gf and anode-off gas Gd, or raw fuel gas Gf and anode-off gas Gd, and its state can change depending on the system's operating state. Similarly, gas Gy for the second burner is either a mixture of air Ac and cathode-off gas Ge, or air Ac and cathode-off gas Ge, and its state can change depending on the system's operating state. In other words, the gas supplied to burner 3 changes its state as appropriate in response to system startup, power generation (full load or partial load), shutdown, etc.

[0056] The raw fuel gas Gf is a type of hydrocarbon-containing gas. On the other hand, air Ac is a type of oxidizer-containing gas. During the combustion operation of burner 3, air Ab is continuously supplied from the burner cooling air line Lh to regulate the combustion temperature.

[0057] The combustion gas Gg produced by combustion in burner 3 is sent to the combustion gas line Lg, and passes sequentially through the heat radiating cylinder Za, combustion gas pipe Zb, evaporator 5, CO oxidizer 8, and evaporator 4 before being discharged to the outside of the hot module HM from the gas outlet D1. As will be described in more detail later, the heat radiating cylinder Za and combustion gas pipe Zb are arranged to effectively heat the reformer 2 using the combustion gas Gg. In addition, the combustion gas Gg in the combustion gas line Lg is used for heat exchange as it passes through evaporators 5 and 4, and if carbon monoxide is present, it is converted to carbon dioxide as it passes through CO oxidizer 8.

[0058] <Hot Module> Next, the configuration of the hot module HM will be explained in more detail. Figure 2 is a perspective view of the hot module HM. Figure 3 is a perspective view of the hot module HM with the first box X1, the second box X2, and a portion of the plate-shaped insulation material 53 omitted to facilitate understanding of the internal structure of the hot module HM. Note that the front / back, left / right, and up / down directions (directions that are orthogonal to each other) in the following explanation are merely defined for convenience, as shown in Figure 2, etc. In this embodiment, the up / down direction coincides with the vertical direction.

[0059] As shown in Figures 2 and 3, the hot module HM comprises a first base X1a, a second base X2a, a first box X1 formed on the first base X1a, a second box X2 formed on the second base X2a, a plurality of first support columns 51 (four in this embodiment) supporting the first base X1a, and a plurality of second support columns 52 (four in this embodiment) supporting the second base X2a.

[0060] The first box X1 is housed inside the second box X2, and in this state, multiple first support columns 51 support the first base X1a from the second base X2a to a predetermined height. The first box X1 is set as a first region R1 (see Figure 1) in which the internal area becomes a high-temperature operating region, and houses the first equipment group GP1 which undergoes chemical reactions inside during the power generation operation of the system. This first equipment group GP1 includes a cell stack 1, a reformer 2, and a burner 3.

[0061] The area inside the second box X2 but outside the first box X1 (below the first base X1a) is set as the second region R2 (see Figure 1), which is a low-temperature operating region, and houses the second equipment group GP2, which does not undergo chemical reactions internally during the system's power generation operation. The second equipment group GP2 includes an evaporator 4 and a heat exchanger (air preheater 5 and anode off-gas cooler 6).

[0062] The second region R2 also houses a third equipment group GP3, which undergoes a chemical reaction internally only when certain conditions are met during the system's power generation operation. The third equipment group GP3 includes a CO oxidizer 8, which does not operate if the oxidation reaction at burner 3 is complete, and only operates if the oxidation reaction at burner 3 is incomplete. Since the CO oxidizer 8 generates only a small amount of heat due to the catalytic reaction, there is virtually no problem in placing the CO oxidizer 8 in the second region R2 (low-temperature operating region), thereby reducing the capacity of the first box X1.

[0063] Plate-shaped insulation material 53 is attached to each side (front, back, left, and right) and the top (upper) of the first box X1. The plate-shaped insulation material 53 covers almost the entire outer surface of the first box X1 (front, back, left, right, and top). This provides a strong insulation effect, making it easy to maintain a high temperature inside the first box X1.

[0064] The space in the second region R2 (the space where the second equipment group GP2 is located) is filled with a granular insulation material (not shown). Although heat conduction occurs from the first box X1, which is a high-temperature operating region, to the second region R2 through the first base X1a, sufficient insulation effect can be obtained by filling it with the granular insulation material. Therefore, the second equipment group GP2 and its connecting piping can be constructed without using expensive high-temperature resistant materials.

[0065] Furthermore, the first base X1a is provided with a pipe insertion hole (through hole), and each line (pipe) extending across the boundary between the first region R1 and the second region R2 is arranged to pass through this through hole. As a result, fluid is transferred between the first equipment group GP1 and the second equipment group GP2 through pipes that penetrate the first base X1a vertically. Thus, in this embodiment, the piping for fluid transfer between the equipment groups GP1 and GP2 is simply a matter of attaching the pipes to the pipe insertion holes drilled in the first base X1a, and therefore does not require any special seals or the like.

[0066] Furthermore, bellows-type expansion joints may be provided in the fluid pipelines passing through the second equipment group GP2. Pipes connecting the pipelines that penetrate the first base X1a to the heat exchangers, and pipes connecting the heat exchangers to each other, expand and contract due to temperature changes between the cold state and operation of the system. The thermal stress generated by this expansion and contraction can cause cracks and ruptures in the pipe body and joints, potentially leading to serious malfunctions such as flammable gas leaks. By including bellows-type expansion joints in the piping equipment used for fluid connections in the second equipment group GP2, the generation of thermal stress can be minimized, making it possible to avoid such malfunctions.

[0067] In this embodiment, as shown in Figure 1, at least in each line of the fluid pipeline passing through the second equipment group GP2 that extends across the boundary between the first region R1 and the second region R2, a bellows-type expansion joint that can expand and contract vertically is installed near the boundary of the second region R2. More specifically, a first bellows-type expansion joint B1 is installed near the boundary of the mixed gas line Lb, a second bellows-type expansion joint B2 is installed near the boundary of the anode-off gas line Ld, a third bellows-type expansion joint B3 is installed near the boundary of the cathode air line Le, and a fourth bellows-type expansion joint B4 is installed near the boundary of the combustion gas line Lg. In addition, bellows-type expansion joints may be installed in each pipe connecting heat exchangers within the second region R2.

[0068] The hot module HM is assembled in the following steps, for example: First, the second equipment group GP2 is placed on the second base X2a, and piping between the equipment is installed using the required piping equipment. Next, multiple first support columns 51 are attached to the second base X2a, and the first base X1a is placed on the tips of the first support columns 51 and fixed in place. Next, conduits are installed in the pipe insertion holes drilled in the first base X1a, and piping is installed between these conduits and the second equipment group GP2. Next, a casing surrounding the second equipment group GP2 is attached to the second base X2a to form a semi-open second box X2, and granular insulation material is filled inside the second box X2.

[0069] Next, the first equipment group GP1 is placed on the first base X1a, and piping is installed between the conduit attached to the first base X1a and the first equipment group GP1, and piping between equipment is installed using the required piping equipment. Then, a casing surrounding the first equipment group GP1 is attached to the first base X1a to form a sealed first box X1, and plate-shaped insulation material 53 is attached to the sides and top of the first box X1. A casing surrounding the plate-shaped insulation material 53 attached to the first box X1 is attached to the semi-open second box X2 to form a sealed second box X2. By going through the above steps, the hot module HM can be easily assembled.

[0070] Figures 4 to 6 are perspective views of the hot module HM from different viewpoints. Figures 7 and 8 are side views of the hot module HM from different viewpoints. In these figures, the first box X1, the second box X2, and the plate-shaped insulation material 53 are not shown in order to facilitate understanding of the internal structure of the hot module HM. The white arrows shown in Figures 5 to 8 schematically represent the flow direction of each fluid.

[0071] As shown in these figures, a cylindrical reformer 2 is positioned vertically above the first base X1a, approximately in the center of the top view, and a burner 3 is positioned above the reformer 2. As will be described in more detail later, the reformer 2, burner 3, and heat radiation cylinder Za are integrally configured as a reformed gas generator.

[0072] On each side of the reformer 2, there is a cell stack assembly 61, which consists of multiple (four in this embodiment) cell stacks 1 stacked vertically. In the area between the left and right cell stack assemblies 61 on the front side of the reformer 2, as shown in Figure 4, the first distribution manifold Ma and the second distribution manifold Mb are arranged so as to extend vertically. The first distribution manifold Ma and the second distribution manifold Mb are arranged adjacent to each other and in the vicinity of the cell stack assemblies 61.

[0073] By arranging the first distribution manifold Ma and the second distribution manifold Mb adjacent to each other, heat exchange occurs between the surfaces of these two distribution manifolds through radiative and convective heat transfer. Furthermore, by arranging each distribution manifold Ma and Mb near the cell stack assembly 61, heat exchange occurs between the surfaces of the equipment through radiative and convective heat transfer. As a result, the temperatures of the anode fuel (reformed gas Gc) and cathode air (air Aa) supplied to the cell stack 1 are made uniform, and these temperatures are raised to near the operating temperature of the cell stack 1, enabling an efficient power generation reaction throughout the entire power generation cell.

[0074] As shown in Figure 6, in the region between the left and right cell stack assemblies 61 at the rear of the reformer 2, the first collection manifold Mc and the second collection manifold Md are arranged to extend vertically. That is, the cell stack assemblies 61, the first collection manifold Mc, and the second collection manifold Md are arranged to surround the outer cylinder 21 of the reformer 2.

[0075] Thus, each cell stack 1, the first collection manifold Mc, and the second collection manifold Md are positioned near the reformer 2, enabling efficient transfer of waste heat from the power generation reaction to the reformer 2. In particular, the first collection manifold Mc plays a role in actively transferring waste heat contained in the anode off-gas Gd to the reformer 2. The second collection manifold Md also plays a role in actively transferring waste heat contained in the cathode off-gas Ge to the reformer 2. As a result, the amount of heat absorbed in the catalyst layer of the reformer 2 increases significantly, improving the efficiency of the steam reforming reaction, reducing the amount of catalyst used, and enabling miniaturization of the reformer 2.

[0076] <Reformer, burner, heat radiation tube> Next, the configuration of the reformer 2, burner 3, and heat radiation cylinder Za will be described in more detail. In this embodiment, the reformer 2, burner 3, and heat radiation cylinder Za are integrally configured as the reformed gas generator RG.

[0077] Figure 9 shows a side view of the reformed gas generator RG, and Figure 10 shows a cross-sectional view of the reformed gas generator RG from the side. Figure 11 shows the detailed configuration near burner 3 in the reformed gas generator RG. In Figure 11, a schematic example of the circuit configuration of the ignition / flame detection circuit 40 is shown.

[0078] In the reformed gas generator RG, the reformer 2 has an outer cylinder 21, an inner cylinder 22, a catalyst packed bed 23, a base end cover plate 24, and an end end cover plate 25.

[0079] The outer cylinder 21 and the inner cylinder 22 are formed in a cylindrical shape with a common axis extending vertically. Their vertical lengths are approximately the same, but the diameter of the outer cylinder 21 is larger than the diameter of the inner cylinder 22. The outer cylinder 21 and the inner cylinder 22 form a double-cylinder reaction vessel 2a, in which the inner cylinder 22 is positioned inside the outer cylinder 21. Between the outer cylinder 21 and the inner cylinder 22, i.e., inside the reaction vessel 2a, is a catalyst-packed bed 23 filled with a catalyst for steam reforming.

[0080] The base end cover plate 24 connects the base ends (upper ends) of the outer cylinder 21 and the inner cylinder 22, sealing the upper side of the reaction vessel 2a, while the end end cover plate 25 connects the end portions (lower ends) of the outer cylinder 21 and the inner cylinder 22, sealing the lower side of the reaction vessel 2a.

[0081] The base end cover plate 24 and the end end cover plate 25 are annular end plates, and the annular end plates have a dish-shaped, semi-elliptical, or approximately semi-elliptical cross-section. By using annular end plates for the cover plates of the reaction vessel 2a, radial expansion and contraction due to temperature changes are absorbed. Therefore, damage or breakage of the reaction vessel 2a due to thermal stress can be more effectively avoided. The above cross-sectional shapes of the end plates are those specified in JIS B 8247 "End plates for pressure vessels", excluding flat end plates.

[0082] Furthermore, a bellows-structured expansion / contraction absorption section 21c is formed in the outer cylinder 21 slightly above the intake port 21a. By providing the expansion / contraction absorption section 21c, expansion and contraction of the outer cylinder 21 due to temporal temperature changes and positional temperature distribution are absorbed. As a result, damage or breakage of the reaction vessel 2a containing the catalyst due to thermal stress can be avoided, and the reaction vessel 2a can be used for a long period of time. It is preferable to use a commercially available bellows-type expansion joint as the expansion / contraction absorption section 21c, and the outer cylinder 21 can be manufactured inexpensively by joining this joint to a straight pipe.

[0083] Furthermore, in the reformed gas generator RG, the burner 3 has a first gas cylinder 31, a second gas cylinder 32, a flame holder 33, and a heat radiation cylinder Za.

[0084] The first gas cylinder 31 and the second gas cylinder 32 are formed in a cylindrical shape with a common axis extending vertically, and the diameter of the second gas cylinder 32 is larger than the diameter of the first gas cylinder 31. The upper part of the first gas cylinder 31 protrudes above the upper end of the second gas cylinder 32, and the lower part of the first gas cylinder 31 is located inside the second gas cylinder 32. The upper end of the first gas cylinder 31 is sealed, and the gap between the first gas cylinder 31 and the second gas cylinder 32 is sealed at the upper end of the second gas cylinder 32.

[0085] The second gas cylinder 32 and the heat radiation cylinder Za are formed from a single pipe, with the lower end of the second gas cylinder 32 connected to the upper end of the heat radiation cylinder Za. By forming the second gas cylinder 32 and the heat radiation cylinder Za from a single pipe in this way, the need for alignment and joining of the two components is eliminated, allowing the burner 3 to be manufactured at a low cost. As shown in Figure 10, the aforementioned first burner gas Gx flows into the upper part of the first gas cylinder 31, and the aforementioned second burner gas Gy flows into the upper part of the second gas cylinder 32.

[0086] The flame holder 33 is connected to the lower end of the first gas cylinder 31 and is formed in a frustoconical shape with its tip widening downwards (downstream of the flow of the gas to be burned). The flame holder 33 also has multiple rows of through holes 33a spaced apart in the widening direction. The outer diameter of the flame holder 33 and the inner diameter of the second gas cylinder 32 are formed to be approximately the same, so that the burner 3 can burn the first burner gas Gx and the second burner gas Gy and form a stable flame over the entire radial cross-section of the inner diameter of the second gas cylinder 32.

[0087] As shown in Figure 11, the burner 3 is equipped with an electrode pair 40x consisting of a first electrode rod 41 and a second electrode rod 42, with the tip of the electrode pair 40x positioned inside the flame holder 33. The first electrode rod 41 is electrically insulated from the first gas cylinder 31, and the second electrode rod 42 is electrically conductive to the first gas cylinder 31.

[0088] The electrode pair 40x is connected to an ignition / flame detection circuit 40 that controls the operation of gas ignition and detects flames, and can be used for both gas ignition and flame detection. The ignition / flame detection circuit 40 has a gas ignition unit 40a, a current detection unit 40b, a first switch 40c1, and a second switch 40c2. When gas ignition is performed, the ignition / flame detection circuit 40 closes the first switch 40c1 and opens the second switch 40c2 to connect the electrode pair 40x to the gas ignition unit 40a, and a high current from the gas ignition unit 40a flows between the electrodes to generate a spark and achieve gas ignition.

[0089] On the other hand, when a flame is detected, the ignition / flame detection circuit 40 opens the first switch 40c1 and closes the second switch 40c2 to connect the electrode pair 40x to the current detection unit 40b, and the current generated by applying a voltage between the electrodes is detected by the current detection unit 40b to determine whether or not there is a flame. In this way, it is possible to detect the presence or absence of a flame by utilizing the conductivity phenomenon of the flame when a voltage is applied between the electrodes.

[0090] Thus, when igniting gas, the burner 3 makes the first electrode rod 41 function as a spark rod and the second electrode rod 42 function as a ground rod. On the other hand, when detecting a flame, the burner 3 makes the first electrode rod 41 function as a flame rod and the second electrode rod 42 function as a ground rod. Therefore, with the burner 3, by configuring the gas ignition mechanism and the flame detection mechanism to be switchable using the electrode pair 40x consisting of the first electrode rod 41 and the second electrode rod 42, reliable and safe combustion operation can be achieved.

[0091] The heat radiation cylinder Za is formed in a cylindrical shape with a common axis with the inner cylinder 22, and the outer diameter of the heat radiation cylinder Za is smaller than the inner diameter of the inner cylinder 22. Furthermore, the upper end of the heat radiation cylinder Za is connected to the lower end of the second gas cylinder 32 inside the inner cylinder 22, and the lower end of the heat radiation cylinder Za protrudes downward from the lower end of the inner cylinder 22. The heat radiation cylinder Za can also be considered as an element of the burner 3.

[0092] The heat radiating tube Za functions as a combustion chamber and a passage for combustion gases in the burner 3, with its surface acting as a heat radiator for combustion. Since the combustion flame of the burner 3 is located inside the heat radiating tube Za, it is possible to efficiently radiate the thermal energy from this combustion flame from the outer surface of the heat radiating tube Za. In this embodiment, since the heat radiating tube Za functions as a combustion chamber tube, even if combustion heat is continuously applied from the inside to the reaction vessel 2a containing the catalyst, damage or breakage of the heat radiating tube Za due to thermal stress can be avoided.

[0093] The heat radiation cylinder Za is inserted into the inner cylinder 22 such that its surface is separated from the inner cylinder 22 along its entire circumferential direction. In this way, a gap is provided between the outer surface of the heat radiation cylinder Za and the inner surface of the inner cylinder 22. Therefore, when heat energy is supplied from the inner cylinder 22 to the catalyst packed bed 23 for the steam reforming reaction, heat transfer occurs by radiant heat transfer from the heat radiation cylinder Za, without the involvement of heat conduction. This makes it possible to use the reaction vessel 2a for a long period of time while avoiding damage or breakage of the reaction vessel 2a containing the catalyst due to thermal stress.

[0094] In the reformer 2, an inlet 21a for mixed gas Gb (a mixture of raw fuel gas Ga and water vapor) is provided near the lower end of the outer cylinder 21, and an outlet 21b for reformed gas Gc is provided near the upper end of the outer cylinder 21. The mixed gas Gb taken in between the outer cylinder 21 and the inner cylinder 22 from the inlet 21a is reformed as it passes through the catalyst packed bed 23 and is removed as reformed gas Gc from the outlet 21b. Thus, in this embodiment, the inlet 21a is provided on the side corresponding to the tip of the heat radiation cylinder Za, and the outlet 21b is provided on the side corresponding to the base end of the heat radiation cylinder Za.

[0095] Here, the thermal energy of the combustion gas Gg is used for endothermic reactions associated with the steam reforming reaction, so the temperature of the combustion gas Gg decreases from the base end to the tip end of the heat radiation cylinder Za. Taking this into consideration, in this embodiment the inlet 21a and outlet 21b are arranged as described above, so the mixed gas Gb flowing in from the inlet 21a is preheated by the lower-temperature combustion gas Gg and then reformed using the thermal energy of the higher-temperature combustion gas Gg.

[0096] The generated reformed gas Gc (gas containing hydrogen and carbon monoxide) is continuously discharged from the outlet 21b and used as the anode fuel gas for each cell stack 1. In this embodiment, the flow of the mixed gas Gb and reformed gas Gc and the flow of the combustion gas are in opposite directions, which allows for an efficient steam reforming reaction.

[0097] However, the arrangement of the inlet 21a and outlet 21b may be reversed from that of this embodiment, with the inlet 21a located on the side corresponding to the base end of the heat radiation cylinder Za and the outlet 21b located on the side corresponding to the tip end of the heat radiation cylinder Za. In this case, the mixed gas Gb flowing in from the inlet 21a is instantaneously preheated by the high-temperature combustion gas Gg, and then reformed using the thermal energy of the combustion gas Gg, which has cooled down slightly. By making the flow of the mixed gas Gb and reformed gas Gc parallel to the flow of the combustion gas Gg in this way, the preheating effect of the mixed gas Gb is enhanced, and it becomes possible to design the evaporator 4 that prepares the mixed gas Gb with reduced heating capacity (heat exchange capacity), which can be expected to reduce the cost of the evaporator 4.

[0098] <Combustion gas pipe> Next, the configuration of the combustion gas pipe Zb will be explained in more detail. Figure 12 is a side view of the hot module HM, with each box X1, X2, plate-shaped insulation material 53, and each manifold Ma to Md omitted from the diagram, in order to make the arrangement of the combustion gas pipe Zb easier to understand.

[0099] As shown in this figure, the combustion gas pipe Zb consists of a U-turn at the top where vertically extending straight pipes are arranged horizontally (i.e., parallel to each other), and is located behind the reformer 2. The left and right straight pipes connected at the top extend from near the bottom end to near the top end of the reformer 2 and are positioned directly opposite the outer cylinder 21 of the reformer 2. As shown by the dashed arrows in Figure 12, the combustion gas Gg flows upward through the right-hand straight pipe and downward through the left-hand straight pipe.

[0100] As a result, the combustion gas Gg generated when burner 3 is operating flows sequentially through the heat radiation tube Za and the combustion gas pipe Zb, allowing combustion heat to be supplied to the reformer 2 simultaneously from both the inside and outside. Consequently, the amount of heat absorbed in the catalyst layer increases, significantly lowering the temperature of the combustion gas Gg. This makes it possible to supply the lower-temperature combustion gas Gg to the preheating heat exchanger, allowing the heat exchanger to be manufactured from inexpensive materials (e.g., SUS321, SUS316L, SUS310S, etc.).

[0101] Furthermore, the significant increase in heat absorption in the catalyst layer improves the efficiency of the steam reforming reaction, thereby reducing the amount of catalyst used and enabling miniaturization of the reformer 2. In this embodiment, the majority of the energy required for the steam reforming reaction in the reformer 2 is supplied by combustion heat. Therefore, the reformer 2 can stably produce reformed gas Gc without depending on the operating temperature of the cell stack 1.

[0102] Furthermore, as shown in Figure 12, the left combustion gas pipe Zb is positioned directly opposite the right side of the left cell stack assembly 61, and the right combustion gas pipe Zb is positioned directly opposite the left side of the right cell stack assembly 61. This allows the fuel cell system 100 to shorten its startup time.

[0103] In other words, in a reformed fuel cell system that utilizes steam reforming, steam (superheated steam) is sometimes used to raise the temperature of the reformer and cell stack during the startup operation of the fuel cell system. In this case, the combustion gas generated by the combustion of the burner is used as the heat source for the evaporator, and steam is generated by heating water inside the evaporator. However, raising the temperature using only steam generally results in a very long startup operation time of 8 hours or more. In this embodiment, however, since the combustion gas pipe Zb is placed near the reformer 2 and the cell stack assembly 61, the cold reformer 2 and cell stack assembly 61 are indirectly heated by heat radiation during burner combustion. Therefore, the startup operation time can be shortened to, for example, around 4 hours.

[0104] In this embodiment, the reformer 2 is located near the cell stack assembly 61, and the waste heat generated by the power generation reaction in the cell stack 1 is also used to supplement the steam reforming reaction in the reformer 2. Therefore, even if the energy loss increases due to deterioration of the power generation cells, the cell stack 1 can be cooled, and the cell stack 1 can be maintained at an appropriate operating temperature.

[0105] Furthermore, in this embodiment, by making the combustion gas pipe Zb a folded pipe, combustion heat can be repeatedly supplied from the outside of the reformer 2, further increasing the amount of heat absorbed in the catalyst layer. As a result, the material cost of the hot module HM can be effectively reduced by reducing the amount of catalyst used and miniaturizing the reformer 2. The straight section of the folded pipe may be laid along the axial direction of the reformer 2, or it may be laid perpendicular to the axial direction of the reformer 2. In addition, in this embodiment, the number of turns of the folded pipe is set to 1, but the number of turns of the folded pipe may be set to multiple.

[0106] <Cell Stack> Next, we will explain the configuration of cell stack 1 in more detail. Figures 13 and 14 are perspective views of cell stack 1, and Figure 14 is a plan view of cell stack 1.

[0107] As shown in Figures 13 to 15, the cell stack 1 comprises a stacked section 75 in which a predetermined number of flat-plate power generation cells are stacked on the left and right sides, a first end plate 76a provided at the left end of the stacked section 75, and a second end plate 76b provided at the right end of the stacked section 75. The first end plate 76a and the second end plate 76b are provided as a pair of end plates facing each other on the left and right sides of the stacked section 75, and are substantially rectangular in shape when viewed from the left.

[0108] Flanged gas ports 72 are located near each of the four corners of the first end plate 76a. Specifically, as shown in Figure 14, a total of four flanged gas ports 72 are provided, consisting of an anode fuel inlet port 72a, a cathode air inlet port 72b, an anode off-gas outlet port 72c, and a cathode off-gas outlet port 72d. Each flanged gas port 72 has a flange portion 72x that extends radially from the entire circumference of the left (outer) edge.

[0109] Furthermore, the cell stack 1 is provided with support plates 71 that are fixed to the edges of the flange portions 72x of each flanged gas port 72. The support plates 71 have through holes formed in them that match the position and size of each flange 72x of each flanged gas port 72, and the outer surfaces of each flange portion 72x are in close contact with the inner surfaces of each through hole.

[0110] On the front side of the laminated section 75, a plate-shaped first power terminal 74a and a second power terminal 74b are arranged, with the top and bottom as the width direction, to output the power generated by the power generation cells of the laminated section 75. The first power terminal 74a and the second power terminal 74b are power terminals with opposite polarities. The first power terminal 74a protrudes forward from the front side of the laminated section 75, with its end 74a1 bent to the left. The second power terminal 74b protrudes forward from a position lower and to the left of the first power terminal 74a on the front side of the laminated section 75, with its end 74b1 bent to the right.

[0111] Thus, the first power terminal 74a and the second power terminal 74b protrude substantially parallel to the stacking surface (a plane perpendicular to the left-right direction) of the flat-plate power generation cell in the stacked portion 75 and in the same direction (forward in this embodiment). The ends 74a1 and 74b1 of each power terminal form a plane facing forward, and their positions are the same in the front-back and left-right directions.

[0112] <Cell stack assembly> Next, the configuration of the cell stack assembly 61 will be described in more detail. Figures 16 and 17 are perspective views of the left stack assembly 61 from different viewpoints. In this embodiment, the cell stack 1 in the right cell stack assembly 61 is arranged in the opposite orientation to the cell stack 1 in the left cell stack assembly 61. As a result, each cell stack assembly 61 provided on the left and right sides of the reformer 2 is configured such that the power terminals 74a and 74b are located at the front, while the flanged gas port 72 is located inward in the left-right direction.

[0113] The stack assembly 61 is constructed by stacking multiple cell stacks 1 vertically using an open rack 62. This makes it possible to minimize the installation area of ​​the cell stack assembly 61, and consequently the installation area of ​​the hot module HM. Therefore, according to this embodiment, a fuel cell system 100 can be constructed that is easy to install in narrow spaces, such as empty spaces in existing facilities. In addition, by mounting multiple cell stack assemblies 61 on the hot module HM, it is easy to increase the power generation output of the fuel cell system 100.

[0114] The open rack 62 has vertically extending column sections 64 at each of the four corners when viewed from above, and multiple stage boards 63 are fixedly supported by these four column sections 64 and arranged at approximately equal intervals in the vertical direction. The size of the space between the stage boards 63 is set to match the size of the cell stack 1.

[0115] Each cell stack 1 is placed on the stage base 63, and a support plate 71 is fixed to the right-side column 64, for example, by screws, and then housed in the open rack 62. Therefore, assembling the cell stack assembly 61 only requires repeating the process of placing the cell stack 1 on the stage base 63 and fixing the support plate 71 to the column 64. This makes it easy to assemble the cell stack assembly 61. In addition, each cell stack 1 is stably supported by its own weight on the stage base 63, held in the correct position in the vertical direction, and prevented from falling off during operation.

[0116] Furthermore, although the open rack 62 described above is designed to accommodate a specified number (four in this embodiment) of cell stacks 1, an open rack assembled from multiple unit racks corresponding to one cell stack 1 may be used instead. Figure 18 illustrates a state in which cell stacks 1 are mounted on a unit rack 62a that can form such an open rack.

[0117] Each unit rack 61a comprises a stage panel 63a, which has the same configuration as one level of the stage panel 63 in the open rack 62, and four column sections 64a, which have the same configuration as one level of the four column sections 64 in the open rack 62, allowing the unit racks 61a to be stacked and fixed in the vertical direction. Thus, similar to the case of the open rack 62, the required number of cell stacks 1 can be housed in each unit rack 61a, and by stacking and fixing the housed unit racks 61a (stack holders), an equivalent to the aforementioned stack assembly 61 can be obtained.

[0118] In this case, the open rack is formed by unit racks 61a, each divided for each cell stack 1. When using unit racks 61a in this way, the number of cell stacks 1 can be easily adjusted, for example, according to the power output of the hot module HM. In addition, since there are no empty spaces in the open rack where cell stacks 1 are not installed, the material cost of the rack can be reduced.

[0119] <Manifold branch pipes> Each flanged gas port 72 in all cell stacks 1 is connected to a branch pipe extending from the corresponding manifold. Specifically, the anode fuel inlet port 72a is connected to a branch pipe extending from the first distribution manifold Ma, the cathode air inlet port 72b is connected to a branch pipe extending from the second distribution manifold Mb, the anode off-gas outlet port 72c is connected to a branch pipe extending from the first collection manifold Mc, and the cathode off-gas outlet port 72d is connected to a branch pipe extending from the second collection manifold Md. In this embodiment, there are eight cell stacks 1, so eight branch pipes extend from each manifold.

[0120] Each branch pipe extending from manifolds Ma to Md has a length longer than the shortest distance connecting the corresponding flanged gas port 72 to the manifold and includes a curved section. Furthermore, each branch pipe is provided with a flange at its end, allowing it to be connected to the flange portion 72x of the corresponding flanged gas port 72.

[0121] Figure 19 shows an example of the configuration of branch pipes extending from each manifold Ma to Md (collectively referred to as "manifold Mx" for convenience). All branch pipes BP shown in this figure extend from manifold Mx and have a flange Fg at their end.

[0122] In the example shown in Figure 19(A), two branch pipes BP extend from a manifold Mx to two cell stacks 1, with one branch pipe BP containing a curved section CV1 and the other branch pipe BP containing a curved section CV2. Both of these curved sections CV1 and CV2 are planar (i.e., two-dimensional) pipe structures. That is, the cross-sectional center of the branch pipe BP (the cross-sectional center when cut by a plane perpendicular to the direction in which the branch pipe BP extends) is contained within the same plane (the plane perpendicular to the axial direction of the manifold Mx) throughout the entire region of the curved section CV1, and the cross-sectional center of the branch pipe BP is contained within the same plane (the plane perpendicular to the axial direction of the manifold Mx) throughout the entire region of the curved section CV2.

[0123] In the example shown in Figure 19(B), a branch pipe BP extends from a manifold Mx to a single cell stack 1, and this branch pipe BP includes a curved section CV3. This curved section CV3 also has a planar pipe structure. That is, the cross-sectional center of the branch pipe BP is contained within the same plane (a plane perpendicular to the axial direction of the manifold Mx) throughout the entire area of ​​the curved section CV3. Furthermore, a bellows-type expansion joint Bp1 is provided in the branch pipe BP, making it possible to absorb the expansion and contraction of the branch pipe BP.

[0124] In the example shown in Figure 19(C), two branch pipes BP extend from the manifold Mx to two cell stacks 1, partially illustrating the configuration. One branch pipe BP includes a curved section CV4, and the other branch pipe BP includes a curved section CV5. Both of these curved sections CV4 and CV5 are three-dimensional pipe structures. In other words, in neither the curved section CV4 nor CV5 are the cross-sectional viewing centers of the branch pipes BP contained within the same plane throughout their entire regions.

[0125] In the example shown in Figure 19(D), two branch pipes BP extend from the manifold Mx to two cell stacks 1, partially illustrating the configuration. One branch pipe BP includes a curved section CV6, and the other branch pipe BP includes a curved section CV7. Both of these curved sections CV6 and CV7 have a three-dimensional pipe structure. That is, in neither of the curved sections CV6 nor CV7, the cross-sectional viewing center of the branch pipe BP is contained within the same plane throughout its entire region.

[0126] As shown in the example in Figure 19(A) or (B), by providing a curved section with a planar pipe structure in the branch pipe BP of the manifold Mx, the expansion and contraction of the pipe, mainly occurring in the horizontal direction of the branch pipe BP (in a direction perpendicular to the vertical direction of the hot module HM), can be effectively absorbed. This eliminates the problem of gas leaks caused by stress acting on the joint with the flanged gas port 72.

[0127] On the other hand, as shown in the example in Figure 19(C) or (D), if a curved section with a three-dimensional pipe structure is provided in the branch pipe BP of manifold Mx, expansion and contraction of the pipe occurring not only in the horizontal direction but also in the vertical direction (up and down direction of the hot module HM) can be effectively absorbed. This eliminates the problem of gas leakage caused by stress acting on the joint with the flanged gas port 72. The type of pipe structure to be provided in the curved section of the branch pipes of each manifold Ma to Md can be determined according to, for example, the specifications of the hot module HM.

[0128] <Power terminals and their connection configurations> Furthermore, in both the left and right stack assemblies 61, each power terminal 74a and 74b in each cell stack 1 protrudes forward, and the ends 74a1 and 74b1 of these power terminals are aligned so that their positions are the same in the front-to-back and left-to-right directions. Also, within the same stack assemblies 61, the vertical positional relationship between the first power terminal 74a and the second power terminal 74b is aligned. That is, in the right stack assemblies 61, the first power terminal 74a is above the second power terminal 74b in every cell stack 1, and in the left stack assemblies 61, the first power terminal 74a is below the second power terminal 74b in every cell stack 1.

[0129] The power terminals 74a and 74b of adjacent cell stacks 1 are electrically connected using a main busbar 78a and a sub-busbar 78b, as shown in Figures 5 and 7, making it possible to combine the power generated by each cell stack 1 and output it externally. The busbars 78a and 78b are connected and fixed to the ends 74a1 and 74b1 of the power terminals, for example, by screws.

[0130] Figure 20 schematically shows the connection configuration of each power terminal 74a, 74b. As shown in this figure, in each cell stack 1 of the cell stack assembly 61 on the right, the first power terminal 74a is located above the second power terminal 74b, and in each cell stack 1 of the cell stack assembly 61 on the left, the first power terminal 74a is located below the second power terminal 74b.

[0131] In the cell stack assembly 61 on the right, the connections between the second power terminal 74b of the top cell stack 1 and the first power terminal 74a of the second cell stack 1 from the top, the second power terminal 74b of the second cell stack 1 from the top and the first power terminal 74a of the third cell stack 1 from the top, and the second power terminal 74b of the third cell stack 1 from the top and the first power terminal 74a of the bottom cell stack 1 are all realized by the main busbar 78a.

[0132] In the cell stack assembly 61 on the left, the connection between the first power terminal 74a of the top cell stack 1 and the second power terminal 74b of the second cell stack 1 from the top, the connection between the first power terminal 74a of the second cell stack 1 from the top and the second power terminal 74b of the third cell stack 1 from the top, and the connection between the first power terminal 74a of the third cell stack 1 from the top and the second power terminal 74b of the bottom cell stack 1 are all realized by the main busbar 78a.

[0133] Furthermore, the second power terminal 74b of the lowest cell stack 1 in the right cell stack assembly 61 and the first power terminal 74a of the lowest cell stack 1 in the left cell stack assembly 61 are realized by a sub-busbar 78b. In addition, the first power terminal 74a of the uppermost cell stack 1 in the right cell stack assembly 61 and the second power terminal 74b of the uppermost cell stack 1 in the left cell stack assembly 61 are each connected to a separate power line 79. These power lines 79 are each protected by a separate power line protection tube 79a and extend outside the hot module HM.

[0134] The main busbar 78a is made of a metal plate having an expansion / contraction absorption section 78a1 to prevent malfunctions caused by vertical expansion and contraction due to the temperature difference between the cold state and power generation operation of the hot module HM. In this embodiment, the expansion / contraction absorption section 78a1 is a U-shaped curved section when viewed from the left or right, as shown in Figure 8, but it may also be a V-shaped bent section or the like. By employing a main busbar 78a with an expansion / contraction absorption section 78a1, thermal stress is alleviated, stable power generation operation can be achieved, and excessive force can be prevented from acting on each stage of the cell stack 1.

[0135] The sub-busbar 78b is made of a metal plate having an expansion / contraction absorption section 78b1 to prevent malfunctions caused by horizontal expansion and contraction due to the temperature difference between the hot module HM when it is cold and when it is operating to generate electricity. In this embodiment, the expansion / contraction absorption section 78b1 is a U-shaped curved section when viewed in the vertical direction, as shown in Figure 5, etc., but it may also be a V-shaped bent section or the like. By using a sub-busbar 78b having an expansion / contraction absorption section 78b1, thermal stress is alleviated, stable power generation operation can be achieved, and excessive force can be prevented from acting on the uppermost cell stack 1.

[0136] <Evaporator> Next, the configuration of the evaporator 4 will be explained in more detail. Figure 21 is a diagram of the configuration of the plate assembly 80 that functions as the evaporator 4, with the left side view shown on the left, the front view in the center, and the right side view on the right.

[0137] The plate assembly 80 is formed by stacking multiple heat transfer plates 81 in the front-to-back direction between a first end plate 82a and a second end plate 82b that are arranged facing each other front to back, and then joining each end plate 82a, 82b and each heat transfer plate 81 together to form a single unit. As will be described later, each of these heat transfer plates 81 has either a low-temperature fluid channel through which the low-temperature fluid (raw fuel gas Ga and reformed water Wa) in the evaporator 4 flows, or a high-temperature fluid channel through which the high-temperature fluid (combustion gas Gg) in the evaporator 4 flows.

[0138] Figure 22 is a perspective view of the heat transfer plate 81. As shown in this figure, the heat transfer plate 81 has a substantially rectangular flat plate portion 81a (heat transfer surface portion) with the vertical direction as its longitudinal direction, and a frame portion 81b that extends from the edge of the flat plate portion 81a to the rear at a substantially uniform height. The front and back surfaces of the flat plate portion 81a function as heat transfer surfaces parallel to the vertical direction.

[0139] A first header forming hole 83a1 and a fifth header forming hole 83e1 are provided in the upper right position of the flat plate portion 81a. Furthermore, a second header forming hole 83b1 is provided in the lower left position of the flat plate portion 81a, a third header forming hole 83c1 is provided in the lower right position of the flat plate portion 81a, and a fourth header forming hole 83d1 is provided in the upper left position of the flat plate portion 81a.

[0140] Each heat transfer plate 81 has predetermined components arranged inside the frame portion 81b to form either a low-temperature fluid flow path shown on the left side of Figure 23 or a high-temperature fluid flow path shown on the right side of Figure 23. An enlarged view of the vicinity of the water distribution plate 86 is shown within the upper frame of Figure 23.

[0141] The components that make up the low-temperature fluid flow path are a meandering flow path plate 85, a water distribution plate 86 (the part outside the dashed line Q1 shown in Figure 23), a third auxiliary plate 87c (the part below the dashed line Q3 shown in Figure 23), and a fourth auxiliary plate 87d (the part above the dashed line Q2 shown in Figure 23, excluding the water distribution plate 86).

[0142] A meandering channel plate 85, widely positioned in the central region of the heat transfer plate 81, has a meandering channel 85a formed therein that extends in a meandering manner from top to bottom. The meandering channel 85a can be formed, for example, by laser cutting, and by manufacturing the meandering channel plate 85 in this manner, mass production is possible with fewer man-hours, and processing costs can be kept low. The meandering channel 85a is generally formed by a series of stages of unit channels Ch, each consisting of an inclined channel section Ch1 that slopes diagonally downward so that fluid flows from one end near the left end and the other near the right end, and a return channel section Ch2 that reverses the fluid flow at the end of the inclined channel section Ch1, which are formed continuously in the vertical direction.

[0143] The water distribution plate 86 is a plate member positioned at a location corresponding to the first header section forming hole 83a1. As shown in the upper frame of Figure 23, it consists of a main hole 86a communicating with the first header section forming hole 83a1 and a peripheral edge 86b surrounding the main hole 86a. A secondary hole 86c is formed in the peripheral edge 86b, penetrating from the inner wall of the main hole 86a outwards. The secondary hole 86c extends downward from the main hole 86a and connects to the upper end 85a1 of the meandering flow channel.

[0144] The third auxiliary plate 87c is positioned below the meandering channel plate 85 and has a third flow hole 89c at a position corresponding to the third header section forming hole 83c1, and a second header section corresponding hole 83b2 at a position corresponding to the second header section forming hole 83b1. The second header section corresponding hole 83b2 is connected to the lower end of the meandering channel 85a.

[0145] The fourth auxiliary plate 87d is positioned above the meandering channel plate 85 and has a fourth flow hole 89d at a position corresponding to the fourth header section forming hole 83d1, and an upper end portion 85a1 of the meandering channel at a position corresponding to the fifth header section forming hole 83e1. The upper end portion 85a1 of the meandering channel is connected to the upper end of the meandering channel 85a in the meandering channel plate 85.

[0146] The components that make up the high-temperature fluid flow path are a heat transfer fin 88, a first auxiliary plate 87a, and a second auxiliary plate 87b. In this embodiment, the heat transfer fin 88 is a corrugated fin with numerous flow paths extending in the vertical direction, and is widely arranged in the central region of the heat transfer plate 81.

[0147] The first auxiliary plate 87a is positioned above the heat transfer fins 88 and has a first flow hole 89a at a position corresponding to the first header section forming hole 83a1, a fifth flow hole 89e at a position corresponding to the fifth header section forming hole 83e1, and a fourth header section corresponding hole 83d2 at a position corresponding to the fourth header section forming hole 83d1. The fourth header section corresponding hole 83d2 is connected to the entire upper end of the heat transfer fins 88.

[0148] The second auxiliary plate 87b is positioned below the heat transfer fin 88 and has a second flow hole 89b at a position corresponding to the second header section forming hole 83b1 and a third header section corresponding hole 83c2 at a position corresponding to the third header section forming hole 83c1. The third header section corresponding hole 83c2 is connected to the entire lower end of the heat transfer fin 88.

[0149] In the plate assembly 80, heat transfer plates 81 with low-temperature fluid channels and heat transfer plates 81 with high-temperature fluid channels are alternately stacked and integrated between each end plate 82a, 82b. In the plate assembly 80 formed in this way, it can also be seen that low-temperature fluid channels are formed on one heat transfer surface side of the heat transfer plate 81 (flat plate portion 81a), and high-temperature fluid channels are formed on the other heat transfer surface side.

[0150] As shown in Figure 21, each end plate 82a, 82b is formed in a substantially plate shape such that its outer edge generally coincides with that of the heat transfer plate 81 when viewed from the front. The first end plate 82a, located at the front, is provided with fluid ports corresponding to the first and fifth header section forming holes 83a1, 83e1, while the second end plate 82b, located at the rear, is provided with fluid ports corresponding to the second, third, and fourth header section forming holes 83b1, 83c1, 83d1.

[0151] As a result, the plate assembly 80 has a first header portion 83a formed by connecting a first header portion forming hole 83a1, a first flow hole 89a, and a main hole 86a in the front-rear direction, and the first header portion 83a opens forward at the first end plate 82a. The plate assembly 80 also has a second header portion 83b formed by connecting a second header portion forming hole 83b1, a second header portion corresponding hole 83b2, and a second flow hole 89b in the front-rear direction, and the second header portion 83b opens rearward at the second end plate 82b.

[0152] The plate assembly 80 also has a third header section 83c formed by connecting a third header section forming hole 83c1, a third header section corresponding hole 83c2, and a third flow hole 89c in the front-rear direction, and the third header section 83c opens to the rear at the second end plate 82b. The plate assembly 80 also has a fourth header section 83d formed by connecting a fourth header section forming hole 83d1, a fourth header section corresponding hole 83d2, and a fourth flow hole 89d in the front-rear direction, and the fourth header section 83d opens to the rear at the second end plate 82b.

[0153] Furthermore, the plate assembly 80 has a fifth header section 83e formed by connecting the fifth header section forming hole 83e1, the fifth flow hole 89e, and the upper end portion 85a1 of the meandering flow path in the front-rear direction, and the fifth header section 83e opens forward at the first end plate 82a. As described above, the first header section 83a and the fifth header section 83e are formed at the upper right end of the plate assembly 80, the second header section 83b is formed at the lower left end of the plate assembly 80, the third header section 83c is formed at the lower right end of the plate assembly 80, and the fourth header section 83d is formed at the upper left end of the plate assembly 80.

[0154] Furthermore, each header section forming hole 83a1 to 83e1, each flow hole 89a to 89e, and each header section corresponding hole 83b2 to 83d2 can be formed, for example, by laser processing. In addition, in the stacking of the heat transfer plates 81, auxiliary plates 87a to 87d are sandwiched at positions corresponding to header section forming holes where fluid distribution / collection is not required (i.e., positions corresponding to the third header section forming hole 83c1 and the fourth header section forming hole 83d1 on the low-temperature fluid flow path side, and positions corresponding to the first header section forming hole 83a1, the second header section forming hole 83b1, and the fifth header section forming hole 83e1 on the high-temperature fluid flow path side).

[0155] The auxiliary plate is connected by joining the header section forming hole and the edge of the flow hole by brazing or the like, thereby preventing unwanted fluid from entering the fluid flow path and allowing for the easy formation of an appropriate header section. By adopting this configuration, the heat transfer plate 81 can be manufactured with a single type of press die, making it suitable for mass production of the evaporator 4. In this embodiment, the meandering flow path plate 85, the water distribution plate 86, the third auxiliary plate 87c, and the fourth auxiliary plate 87d are all manufactured integrally by punching out a single sheet of material using laser processing or the like. By manufacturing each of these parts integrally in this way, the number of parts can be reduced, thereby reducing the assembly man-hours for the evaporator 4.

[0156] Reformed water Wa is supplied to the first header section 83a, and raw fuel gas Ga is supplied to the fifth header section 83e. The reformed water Wa supplied to the first header section 83a is evenly distributed to the water distribution plate 86 in each low-temperature fluid channel and flows down to the uppermost stage of the meandering channel 85a through the main hole 86a and sub-hole 86c. As this reformed water Wa travels through the meandering channel 85a, it is heated and turns into steam, which reaches the second header section 83b.

[0157] The sub-holes 86c in the water distribution plate 86 may be configured to extend upward from the main hole 86a, then pass through a return channel and connect to the upper end 85a1 of the meandering channel. By discharging the modified water Wa supplied to the main hole 86a upward, relatively high flow resistance is generated when pushing the modified water Wa out from the sub-holes 86c. Therefore, compared to the configuration in which the modified water Wa is discharged downward as shown in Figure 23, a more uniform water distribution becomes possible.

[0158] The raw fuel gas Ga supplied to the fifth header section 83e is also evenly distributed to each low-temperature fluid channel and heated as it travels through the meandering channel 85a simultaneously with the reformed water Wa, before reaching the second header section 83b. In this way, the plate assembly 80 is configured to allow water evaporation in the raw fuel gas Ga, and a mixed gas Gb of raw fuel gas Ga and water vapor is continuously obtained in a superheated state in the second header section 83b. This mixed gas Gb can then be supplied directly to the reformer 2.

[0159] Meanwhile, combustion gas Gg is supplied to the third header section 83c as a heat source gas. The combustion gas Gg supplied to the third header section 83c is evenly distributed to each high-temperature fluid flow path, flows through each of the flow paths in the heat transfer fins 88 in an upward flow, is collected in the fourth header section 83d, and discharged into the pipeline Lg1.

[0160] At this time, the meandering paths 85a of each low-temperature fluid channel face each other in the front-to-back direction via the heat transfer fins 88 and heat transfer plates 81 of the adjacent high-temperature fluid channel, so that the reformed water Wa and raw fuel gas Ga are efficiently heated using the heat of the combustion gas Gg.

[0161] Furthermore, since the reformed water Wa and raw fuel gas Ga flow downward through the meandering path 85a, and the combustion gas Gg flows upward through the heat transfer fins 88, heat exchange occurs in a counterflow manner. As a result, in the lower region of the plate assembly 80, the steam (reformed water Wa) is heated by the high-temperature heat source gas (combustion gas Gg) immediately after introduction from the third header section 83c, allowing superheated steam to be extracted from the second header section 83b. This superheated steam is useful in the steam reforming reaction of hydrocarbon fuels in the reformer 2.

[0162] <Effects of the present invention and other variations> As described above, the hot module HM according to this embodiment comprises a double-cylinder reformer 2 having a catalyst packed bed 23 between an outer cylinder 21 and an inner cylinder 22, a heat radiation cylinder Za inserted into the inner cylinder 22 so that their surfaces are spaced apart, a burner 3 connected to the heat radiation cylinder Za, a cell stack assembly 61 which integrates a plurality of fuel cell cell stacks 1, a first distribution manifold Ma which serves as the introduction main pipe for anode fuel Gc, a second distribution manifold Mb which serves as the introduction main pipe for cathode air Aa, a first collection manifold Mc which serves as the outlet main pipe for anode off-gas Gd, and a second collection manifold Md which serves as the outlet main pipe for cathode off-gas Ge, and the cell stack assembly 61, the first collection manifold Mc, and the second collection manifold Md are arranged to surround the outer cylinder 21.

[0163] The combustion gas Gg generated when burner 3 is operating flows through the heat radiation cylinder Za, supplying combustion heat to the reformer 2 from the inside. Meanwhile, multiple cell stacks 1, the first collection manifold Mc, and the second collection manifold Md supply waste heat from the outside of the reformer 2 associated with the power generation reaction. The first collection manifold Mc plays a role in actively supplying waste heat contained in the anode off gas Gd to the reformer 2. The second collection manifold Md plays a role in actively supplying waste heat contained in the cathode off gas Ge to the reformer 2. As a result, the amount of heat absorbed in the catalyst packed bed 23 increases significantly, improving the efficiency of the steam reforming reaction. Consequently, the amount of catalyst used is reduced, and the reformer 2 can be made smaller.

[0164] Furthermore, the surface of the inner cylinder 22 and the surface of the heat radiation cylinder Za are spaced apart. In other words, the transfer of combustion heat is carried out by radiative heat transfer and does not involve heat conduction. As a result, the reformer 2 is lessened from stress due to thermal stress, and can be used for a long period of time while avoiding damage or breakage.

[0165] Furthermore, since the power generation reaction in SOFC cell stack 1 occurs on the anode, most of the reaction energy is derived from waste heat contained in the anode off-gas Gd. The energy required for the steam reforming reaction is largely supplied by combustion heat and waste heat contained in the anode off-gas Gd. Therefore, reformer 2 can stably produce reformed gas (anode fuel) Gc without depending on the operating temperature of cell stack 1.

[0166] Furthermore, in the hot module HM, the first distribution manifold Ma and the second distribution manifold Mb are placed adjacent to each other and near the cell stack assembly 61. By placing the first distribution manifold Ma and the second distribution manifold Mb adjacent to each other, heat exchange occurs between the surfaces of the two distribution manifolds Ma and Mb through radiative and convective heat transfer. Also, by placing each distribution manifold Ma and Mb near the cell stack assembly 61, heat exchange occurs between the surfaces of the equipment through radiative and convective heat transfer. As a result, the temperatures of the anode fuel Gc and cathode air Aa supplied to the cell stack 1 are made uniform and raised to near the operating temperature of the cell stack 1, so that the power generation reaction can be carried out efficiently throughout the power generation cell.

[0167] In the hot module HM, the cell stack 1 has a predetermined number of flat-plate power generation cells stacked between a pair of end plates 76a and 76b, and one end plate (first end plate 76a) has ports for anode fuel inlet 72a, cathode air inlet 72b, anode off-gas outlet 72c, and cathode off-gas outlet 72d. Furthermore, each of these ports is connected to the corresponding first distribution manifold Ma, second distribution manifold Mb, first collection manifold Mc, and second collection manifold Md via branch pipes BP, and each of the branch pipes BP has a pipe length longer than the shortest distance connecting the port to the manifold and is configured to include a curved section CV.

[0168] For each of the multiple cell stacks 1 that make up the cell stack assembly 61, gas is introduced from the main distribution manifolds Ma and Mc via the branch pipe BP, while gas is discharged from each cell stack 1 to the main collection manifolds Mc and Md via the branch pipe BP.

[0169] Here, the branch pipe BP expands and contracts due to temperature changes between the system's cold state and operation. The thermal stress generated by this expansion and contraction can cause cracks and ruptures in the pipe body and connections (especially at the connections to the ports), potentially leading to serious malfunctions such as flammable gas leaks. To suppress such malfunctions, in this embodiment, for example, the anode fuel inlet port 72a and the first distribution manifold Ma (anode fuel introduction main pipe) are connected by the branch pipe BP. However, this branch pipe BP is not a straight pipe of the shortest distance, but rather a pipe structure that includes a curved section CV. Therefore, the expansion and contraction of the pipe can be absorbed by the curved section CV, and the generation of thermal stress is avoided.

[0170] Furthermore, when a branch pipe BP is adopted, for example, in the form shown in Figure 19(A) or (B), the curved sections CV1 to CV3 of the branch pipe BP have a planar pipe structure. This allows for effective absorption of expansion and contraction of the pipe in a predetermined two-dimensional direction (e.g., the horizontal direction). Moreover, when a branch pipe BP is adopted, for example, in the form shown in Figure 19(C) or (D), the curved sections CV4 to CV7 of the branch pipe BP have a three-dimensional pipe structure. This allows for effective absorption of expansion and contraction of the pipe in any direction in three dimensions. When expansion and contraction of the pipe are effectively absorbed in this way, the problem of gas leakage caused by stress acting on the joint with the flanged gas port 72 is eliminated.

[0171] Although the system in this embodiment is a single-stage fuel cell system, the present invention is also applicable to multi-stage fuel cell systems. For example, in a two-stage fuel cell system, a front-stage cell stack and a rear-stage cell stack are provided, and the rear-stage cell stack is configured to generate electricity using the anode off-gas (containing unreacted fuel components) discharged from the front-stage cell stack.

[0172] Although embodiments of the present invention have been described above, the configuration of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. In other words, the above embodiments should be considered to be illustrative in all respects and not restrictive. The technical scope of the present invention is indicated not by the above description of embodiments, but by the claims, and should be understood to include all modifications that fall within the meaning and scope equivalent to the claims. [Industrial applicability]

[0173] This invention is applicable to solid oxide fuel cell systems. [Explanation of symbols]

[0174] 1 Cell Stack 2. Reformer 2a Reaction vessel 3 burners 4. Evaporator 5. Air preheater 6. Anode Off-Gas Cooler 7. Anode-off gas condenser 8 CO Oxidizer 9. Condensate recovery tank 10. No. 1 Fuel Blower 11. First air blower 12 Water pumps 13. Second Nuclear Fuel Blower 14. Second air blower 15 Power Conditioner 16 System Controllers 21 Outer cylinder 21a Inlet 21b Outlet 21c stretchable absorbent part 22 Inner cylinder 23 Catalyst packed bed 24 Proximal cover plate 25 Distal cover plate 31. First gas cylinder 32 Second Gas Canister 33 Flame holder 40 Ignition / Flame Detection Circuit 40a Gas ignition unit 40b Current detection unit 40c1 1st switch 40c2 Second Switch 40x electrode pair 51 1st pillar 52 Second pillar 53. Plate-shaped insulation material 61 Cell Stack Assembly 62 Open Racks 62a Unit Rack 63 Stage Disc 63a Stage Disc 64 Column section 64a Pillar 71 Support plate 72 Flanged Gas Port 72a Anode fuel inflow port 72b Cathode air inlet port 72c Anode Off-Gas Outlet Port 72d Cathode-off gas outlet port 72x Flange section 74a 1st power terminal 74a1 End of the first power terminal 74b Second power terminal 74b1 End of the second power terminal 75 Laminated section 76a 1st end plate 76b 2nd end plate 78a Main bus bar 78a1 Stretchable absorbent part 78b Subbus bar 78b1 Stretchable absorbent part 79 Power lines 79a Power line protection tube 80 Plate Assembly 81 Heat transfer plate 81a Flat plate part 81b Frame 82a First End Plate 82b Second End Plate 83a First Header Section 83b Second Header Section 83c Third Header Section 83d Fourth Header Section 83e Fifth Header Section 83a1 Hole forming the first header section 83b1 Hole forming the second header section 83c1 Hole forming the third header section 83d1 Hole forming the fourth header section 83e1 Fifth header section forming hole 83b2 Hole corresponding to the second header section 83c2 Third Header Corresponding Hole 83d2 Hole corresponding to the 4th header section 85. Meandering channel plate 85a Meandering channel 86 Water distribution plate 86a Main hole 86b Periphery 86c secondary hole 87a First auxiliary plate 87b Second auxiliary plate 87c Third auxiliary plate 87d 4th auxiliary plate 88 heat transfer fins 89a 1st circulation hole 89b 2nd circulation hole 89c 3rd circulation hole 89d 4th circulation hole 89e 5th circulation hole 100 Fuel Cell Systems Aa~Ac Air B1 First bellows-type expansion joint B2 Second bellows type expansion joint B3 Third bellows type expansion joint B4 Fourth bellows type expansion joint BP branch pipe Bp1 Bellows-type expansion joint CV curved section Ch Unit channel Ch1 Inclined channel section Ch2 Folding channel section D1 Gas outlet E1, E2 fuel intake E3, E4 air intake Fg flange Ga raw fuel gas Gb mixed gas Gc reformed gas Gd anode off gas Re Cathode Off-Gas Gf raw fuel gas Gg combustion gas La raw material fuel line Lb mixed gas line Lc Anode Fuel Line Ld Anode Off-Gas Line Ld1 conduit Le Cathode Air Line Le1 conduit Le2 Bypass Route Lf Cathode Off-Gas Line Lf1 conduit Lg combustion gas line Lg1 conduit Lh burner cooling air line Li-treated water line LJ Startup Air Line Lw condensate recovery line Ma 1st Distribution Manifold Mb 2nd Distribution Manifold Mc First Collection Manifold Md Second Collection Manifold RG reformed gas generator Sa air / water separation section Sb Water Level Detector Sc drain valve Wa (modified water) Wb condensed water X1 Box 1 X1a 1st Base X2 Box 2 X2a 2nd Base Za Heat Radiation Tube Zb Combustion gas pipe

Claims

1. A reformer with a double-cylinder structure having a catalyst packed layer between the outer cylinder and the inner cylinder, A heat radiation cylinder is inserted into the inner cylinder such that its surfaces are spaced apart from each other, A burner connected to the heat radiation cylinder, A cell stack assembly formed by integrating multiple fuel cell cell stacks, An anode fuel introduction main pipe arranged along the reformer, comprising a first distribution manifold connected to each of the fuel cell stacks via branch pipes, A cathode air introduction main pipe arranged along the reformer, comprising a second distribution manifold connected to each of the fuel cell stacks via branch pipes, An anode off-gas outlet main pipe arranged along the reformer, comprising a first collection manifold connected to each of the fuel cell stacks via branch pipes, A cathode-off gas outlet main pipe arranged along the reformer, comprising a second collection manifold connected to each of the fuel cell stacks via branch pipes, A hot module for a fuel cell system, characterized in that the cell stack assembly, the first collection manifold, and the second collection manifold are arranged near the reformer and surrounding the outer cylinder, thereby supplying waste heat contained in the anode off-gas from the first collection manifold to the reformer, and supplying waste heat contained in the cathode off-gas from the second collection manifold to the reformer.

2. The hot module according to claim 1, characterized in that the first distribution manifold and the second distribution manifold are arranged adjacent to each other and near the cell stack assembly, thereby enabling heat exchange between the surfaces of the first distribution manifold, the second distribution manifold, and the cell stack assembly.

3. The aforementioned fuel cell stack is A predetermined number of flat-plate type power generation cells are stacked between a pair of end plates, and the end plates have ports for anode fuel inlet, cathode air inlet, anode off-gas outlet, and cathode off-gas outlet. Each of the aforementioned ports is: The corresponding first distribution manifold, second distribution manifold, first collection manifold, and second collection manifold are connected via the branch pipes, The hot module according to claim 1 or 2, characterized in that each of the branch pipes has a pipe length longer than the shortest distance connecting the port and the manifold and includes a curved section.

4. The hot module according to claim 3, characterized in that the curved portion has a planar pipe structure in which the cross-sectional centers of the branch pipes are included in the same plane throughout the entire region of the curved portion.

5. The hot module according to claim 3, characterized in that the curved portion has a three-dimensional pipe structure in which the cross-sectional viewing centers of the branch pipes are not included in the same plane throughout the entire region of the curved portion.

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